1. Field
The present invention relates generally to synchronization in communication systems, and more specifically to system frame number error detection.
2. Background
Many wireless communication systems employ communication protocols that arrange control information and data into frames where an access terminal (user communication device) references the timing of reception and transmission tasks based on a system frame number (SFN). An access terminal, for example, may access information transmitted from a communication network within a particular frame referenced to the current (SFN). Accordingly, the access terminal must maintain frame synchronization with a communication network by tracking and updating the SFN in order to properly receive information. For example, in an asynchronous communication system such as system operating in accordance with WCDMA standards, a base station pages the access terminal during Paging Occasions that are based on the SFN of the cell at the particular time. The access terminal deciphers a frame of a Page Indicator Channel (PICH) where the frame is based on the current SFN. If the SFN of the access terminal is not synchronized to the SFN of the cell, the access terminal will not receive a page and will not be able to receive calls. One potential method for maintaining SFN synchronization between the access terminal and the cell includes requiring the access terminal to constantly monitor a Broadcast Channel (BCH) where each BCH block includes an encoded SFN. Unfortunately, this technique is not practical due to the resulting power consumption and negative impact on battery life of the access terminal. Some conventional systems allow the access terminal to rely on the SFN that is maintained at the access terminal without monitoring the BCH. This technique is limited since if the SFN is incorrect at the access terminal, the access terminal will not be able to receive calls or otherwise maintain frame synchronization with the communication network.
Accordingly, there is a need for system frame number (SFN) evaluation.